diff --git a/sys/dev/ath/if_ath.c b/sys/dev/ath/if_ath.c
index 4105fd68d1e4..e1d2c0fb218f 100644
--- a/sys/dev/ath/if_ath.c
+++ b/sys/dev/ath/if_ath.c
@@ -39,6 +39,11 @@ __FBSDID("$FreeBSD$");
 
 #include "opt_inet.h"
 #include "opt_ath.h"
+/*
+ * This is needed for register operations which are performed
+ * by the driver - eg, calls to ath_hal_gettsf32().
+ */
+#include "opt_ah.h"
 #include "opt_wlan.h"
 
 #include <sys/param.h>